The present invention relates generally to disc drives, and more particularly to a pivot cartridge assembly with vibration reduction features for use in a disc drive.
A disc drive typically has one or more data storage discs mounted on a spindle motor for rotation. Data is read from or written to a plurality of concentric tracks on the discs by an array of read/write heads. These heads are supported by actuator arms controllable by an actuator assembly such that the heads can be positioned at the desired track for each read/write activity.
All disc drives experience some vibration from the various moving parts or vibrations induced by electronic switching. At the same time, in response to the demand for more data storage capacities and shorter seek response time, the discs are configured with increasingly higher track densities and the actuator arms are made relatively light to minimize seek response time. Under such conditions, the effect of vibration is magnified and precise motion control of the actuator arms becomes difficult, especially in the face of increasingly high expectations of shorter seek response time and accuracy in head positioning.
The mechanism that supports the rotational motion of the head positioning actuator is the pivot cartridge assembly which is a major component in the disc drive. The performance of the pivot cartridge assembly is therefore critical to the overall performance of the disc drive, affecting among other things, seek response time and resonance in the actuator assembly.
One conventional method of improving the performance of the pivot cartridge assembly is by securing the upper end of the pivot bearing shaft to the cover of the housing. However, this tends to increase the acoustics level of the disc drive as the cover will serve as a vibrative diaphragm.
The U.S. Pat. No. 5,825,585 issued Oct. 20, 1998, to Tabrizi for xe2x80x9cLaterally Constrained and Damped Mount for a Hard Disk Drivexe2x80x9d describes a shaft which is secured to the cover of the housing by a resilient shaft mount. Whilst this may improve the natural frequency mode in the axial direction of the shaft, it nevertheless fails to address the resonance problems in the radial direction.
Another approach to vibration control is disclosed in the U.S. Pat. No. 5,930,071 issued Jul. 27, 1999, to Back for xe2x80x9cDisk Drive Assembly with Vibration Dampening Pivot Assemblyxe2x80x9d. This document describes the bonding of a rubber-like material to surfaces which are part of a xe2x80x9cbond jointxe2x80x9d, a xe2x80x9cbond jointxe2x80x9d referring to either the joint between the pivot shaft and the inner race of the pivot bearing or the joint between the outer race of the pivot bearing and the pivot housing.
It is a challenge to implement damping techniques that do not involve additional housing members, couplings and rubber interfaces. More often than not, these components require elaborate manufacturing processes or additional sub-assemblies which will decrease the production yield.
There is therefore a need for improved vibration control in a disc drive. It will be evident from the following description that the present invention offers this and other advantages over the prior art.
The present invention provides for the coupling of an upper end of the pivot bearing shaft to the cover of the disc drive in such a manner that the resonance characteristics of the pivot bearing assembly is improved in both the axial and radial direction of the pivot bearing shaft. A damper is located between the pivot bearing shaft and the cover such that the pivot bearing shaft and the cover do not come into direct contact. In addition, the assembly is configured and arranged for the cover to exert restraining forces on the pivot bearing shaft in the radial direction, indirectly through the damper. The damper comprises a sleeve for abutment against the rim of a hole in the cover and against the side of the pivot bearing shaft. The damper may further include a recess for receiving the pivot bearing shaft. The damper may also have a hole in a wall of the recess for receiving a fastener.
In another aspect, the present invention provides for a method of dampening vibration in a disc drive by fitting a damper between an upper end of the pivot bearing shaft and the cover such that the damper is in direct contact with the pivot bearing shaft and with the rim of an opening in the cover of the disc drive.